Abstract
Purpose
To investigate a new MR‐imaging protocol defined as subtraction MR‐fistulography for the detection of fistula‐in‐ano.
Materials and Methods
A total of 36 patients (18 men, 18 women) with the clinical diagnosis of anal fistula or abscess who were scheduled for surgical exploration were preoperatively imaged at 1.5 T in the supine position; coronal STIR sequences and axial T1‐weighted three‐dimensional FLASH sequences before and after intravenous injection of gadobenate dimeglumine (Gd‐BOPTA) were obtained. Image subtraction was routinely used. The image findings were compared with the findings at surgical exploration according to a uniform classification system.
Results
A total of 46 fistulas were seen on subtraction MR‐fistulography, whereas surgery described 41 fistulas. MRI and surgery concordantly depicted a total number of 40 fistulas, six fistulas were only described by MRI, and one fistula was only seen during surgery. A total of 27 abscesses were detected with MRI, compared to 22 during surgery. A total of 22 abscesses were concordantly diagnosed. Complete agreement between subtraction MR‐fistulography and surgery occurred in 32 (89%) of the 36 patients. The four patients in whom both procedures disagreed had complex anal sepsis with multiple fistulas and/or abscesses due to Crohn disease.
Conclusion
High‐resolution subtraction MR‐fistulography is an important complement to surgical exploration and especially suitable for investigating complex anal sepsis. J. Magn. Reson. Imaging 2004;19:91–98. © 2003 Wiley‐Liss, Inc.